New micro-magnetometer device is made from high-temperature superconductor
New micro-magnetometer device is made from high-temperature superconductor lead image
Superconducting quantum interference devices (SQUIDs) are capable of sensitive magnetic flux detection. They have uses in a variety of fields, including medicine and materials science. To reduce magnetic flux noise, the size of SQUIDs can be reduced, but this also decreases the field sensitivity.
In a letter by Cho et al., the authors use a helium ion beam to create a small, yet sensitive, SQUID magnetometer from a high-Tc superconductor. The resulting device has a sensing area of 100 square microns. The process begins by depositing a 35-nanometer-thick film of a superconducting material, YBa2Cu3O7-x, onto cerium oxide buffered sapphire. A helium ion beam then patterns a 250-nanometer layer of gold that is added for electrical contacts. The irradiation converts superconducting material to an insulator without etching or removing any of the superconductor.
Most commercial SQUID magnetometers are made from low-temperature superconductors. Since these, of course, require low temperatures for operation, a way to extend production to high-Tc superconductors is desirable. Many difficulties arise, however, when using high-Tc materials such as cuprates, which are brittle ceramics not easily made into wires or multilayer structures.
One approach tried in the past is to bond a multiturn flux transformer on a separate chip to a single layer SQUID in a flip-chip configuration. This still requires multilayer deposition, leading to complexity and high cost. The present approach is a promising alternative. Initial electrical measurements with the new device showed a reasonable magnetic sensitivity and low noise level, and may suggest a new way to produce high-Tc devices with micron-sized sensors.
Source: “Direct-coupled micro-magnetometer with Y-Ba-Cu-O nano-slit SQUID fabricated with a focused helium ion beam,” by Ethan Y. Cho, Hao Li, Jay C. LeFebvre, Yuchao W. Zhou, R. C. Dynes, and Shane A. Cybart, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5048776 .
